Technical Field
The present invention relates to a sealant film used to constitute a packaging material for a power storage device, a packaging material for a power storage device using the sealant film, a power storage device constituted by using the packaging material, and a method for producing a resin composition for the sealant film.
In this specification and claims, the term “melting point” denotes a melting peak temperature measured by a differential scanning calorimetry (DSC) in accordance with JIS K7121-1987, and the term “crystal melting energy” denotes melting heat (crystal melting energy) measured by a differential scanning calorimetry (DSC) in accordance with JIS K7122-1987.
Further, in this specification and claims, it is intended that the term “crystal melting energy” refers to a value of the highest crystal melting energy when there exists two or more crystal melting peak curves and there also exist two (ΔHm1, ΔHm2) or more crystal melting energy.
Further, in this specification and claims, the term “polymer component” does not include neither of “first elastomer-modified olefin based resin” and “second elastomer-modified olefin based resin”.
Further, in this specification and claims, although “olefin based elastomer” and “styrene based elastomer” are defined, the elastomer containing both olefin and styrene is defined to be classified (categorized) into (defined to belong to) the “styrene based elastomer”.
Further, in this specification and claims, the term “aluminum” is used to include the meaning of aluminum and its alloys.
Description of the Related Art
The following description of related art sets forth the inventors' knowledge of related art and certain problems therein and should not be construed as an admission of knowledge in the prior art.
A lithium-ion secondary battery is widely used as an electric power source for, e.g., a notebook computer, a video camera, a mobile phone, and an electric-powered vehicle. As the lithium-ion secondary battery, a battery structured such that a periphery of a battery body part (main body part including the positive electrode, the negative electrode, and the electrolyte) is surrounded by a case is used. As the material for the case (packaging material), for example, a material structured such that an outer layer made of a heat-resistant resin film, an aluminum foil layer, and an inner layer made of a thermoplastic resin film are integrally bonded in this order is well-known.
A power storage device is structured such that a power storage device body is sandwiched by a pair of packaging materials and the peripheral edge parts of the pair of packaging materials are fusion bonded (heat sealed) to be sealed.
In the meantime, in a lithium-ion secondary battery, etc., the battery body part tends to generate a gas when excessively charged or excessively raised in temperature. For this reason, in some cases, the gas is gradually accumulated in an inner space covered by the packaging material, causing an increased inner pressure of the inside of the packaging material. Since there is a concern that the increase in inner pressure causes bursting of the packaging material, a technology of preventing such bursting of the packaging material has been proposed.
For example, Patent Document 1 (Japanese Unexamined application publication No. 2012-156404) discloses a power storage device equipped with an explosion-proof function. The power storage device includes an electrode laminated body in which sheet-shaped positive electrodes and negative electrodes are laminated via separators. The electrode laminated body is accommodated in a metal laminated film container together with electrolyte. The container is liquid-tightly sealed by a heat sealed portion formed by heat sealing the metal laminated film in a strip-shaped manner along the outer peripheral edge of the container. The power storage device is equipped with a perforating device including a blade support fixedly secured with the outer peripheral edge part of the container pinched and a blade member supported by the blade support and arranged at a center side position than the heat sealed portion of the container. The blade support is configured to move in the outer peripheral direction of the container by being pushed out by the container expanded and deformed at the time of gas generation, so that the blade member is moved together with the blade support to cut though the container.
Further, Patent Document 2 (Japanese Unexamined Application Publication No. 2012-156489) discloses an electric storage element. This electric storage element is provided with an electric storage element body in which electrolyte is impregnated, a packaging member sealing the electric storage element body, a first gas release mechanism arranged inside the packaging member, and a second gas release mechanism arranged outside the packaging member. It is configured such that gas from the inner space of the packaging member accommodating the electric storage element body sequentially passes through each of the gas release mechanisms to thereby allow the gas release from the inner space to the outer space. Further, the electric storage element is provided with a pressure adjustment device that prevents the intrusion of gas from the outer space to the inner space by each of the gas release mechanisms. Between the gas release mechanisms, a buffer space individually partitioned by each of the gas release mechanisms is formed.
However, as described in Patent Document 1, in the case of providing the perforating device including the blade support and the blade member, there are problems such that a new step for providing the perforating device will be required, the production step becomes complicated, and the productivity deteriorates. Further, it is required to provide a structural part, i.e., the perforating device, the cost increases correspondingly.
Further, as described in Patent Document 2, in the case of providing a safety valve mechanism (gas release mechanism, etc.) for releasing the gas generated in the packaging member to the outside of the packaging member, there are problems such that a new step for providing the safety valve mechanism is required, and the productivity deteriorates. Further, it is required to provide a new structural part, i.e., a safety valve mechanism, the cost increases correspondingly.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present disclosure. For example, certain features of the preferred described embodiments of the disclosure may be capable of overcoming certain disadvantages and/or providing certain advantages, such as, e.g., disadvantages and/or advantages discussed herein, while retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.